What is the difference between ovarian cysts and ovarian cancer?

by Dr. Thomas deHoop – Kalispell OB/GYN


I had a pelvic ultrasound that showed an ovarian cyst. In 4 weeks, I will have another follow up ultrasound. What is the difference between ovarian cysts and ovarian cancer? Are they the same or two different topics?


In a woman of reproductive age who has not gone through menopause, ovarian cysts are a normal, natural, monthly occurrence. Every month the ovary develops an egg to release for fertilization. This egg develops into a cyst that reaches its maximum size in the middle of the cycle (about 14 days prior to menses in a normal 28 day cycle) that ruptures and releases the egg. For the next 14 days before the menses, the ruptured cyst can continue as a different cyst that produces hormones to prepare the lining of the uterus for implantation of a pregnancy.  These cysts are usually complex, meaning their walls may be thick or irregular in contour.  A complex cyst may have septations in the center that divides the cysts into compartments, or the fluid may look like it layers out with different densities or debris.  If pregnancy doesn’t occur, then the cyst resolves, the hormones decline initiating a menstrual period.  So, you can see that an ovarian cyst can be normal. This is why when they are initially seen, it is best to repeat the ultrasound in 4-6 weeks to look for resolution as most of these will resolve spontaneously.  This prevents unnecessary intervention.  Abnormal cysts are those that are large (greater than 8-10 centimeters), persist for months, or are associated with significant pain. Despite that, the vast majority of abnormal cysts are not cancerous. So, ovarian cancer can present as cysts but not all ovarian cysts are cancerous; in fact, the vast majorities are benign.
In women who have entered menopause, cysts are much less common.  The ovary is no longer producing eggs for ovulation, so a monthly cyst is not produced.  Some cysts, simple cysts, can be common and benign.  A simple cyst has a thin wall, no sepations and the fluid is homogeneous.  These cysts can be watched safely if there are no other concerns.  Any complex cyst or solid mass in the ovary of a postmenopausal woman needs to be considered for removal if there is any question that it could be malignant.

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PLEASE NOTE: This information is not intended to be medical advice.  It is general health information and does not take into account your particular health status nor is it a substitute for personal medical care.  Kalispell OB/GYN shall not be liable for any damages arising out of the use of the content herein.